1. Field of the Invention
The present invention relates to a novel process for preparing 2-acetonaphthones by cyclizing a ketal or acyl-substituted benzalacetones.
2. Description of the Prior Art
2-Acetonaphtones are very useful as drug intermediates. Heretofore, 2-acetonaphthones have been prepared by processes described in the forementioned references and in U.S. Pat. No. 4,593,125 and J. A. Hyatt and P. W. Raynolds, J. Org. Chem., 49, 384 (1984) and German Pat. Nos. 3,519,009 and 3,518,668. The present invention provides an alternative, more expedient, and economical route for the preparation of these compounds.
Substituted 2-acetonaphthones are also useful as polymer intermediates in the chemical industry, particularly for the preparation of substituted 2-naphthanoic acids and esters thereof. However, the methodology for making 2-naphthanoic acids and esters thereof is very sparse. The major problem posed by the synthesis of these compounds is that, for the 2-naphthanoic acid derivatives to be useful as polymer intermediates, a second functional group besides the carboxyl group must be present. Moreover, such a functional group must be present at a specific location on the molecule. Thus, a single, specific isomer of a substituted 2-naphthanoic acid or ester thereof must be produced out of a large number of distinguishable isomeric naphthanoic acids. The development of such a process is, therefore, of great significance to the industry.
Specific 2-naphthanoic acids have been synthesized by the prior art. For example, see U.S. Pat. Nos. 4,594,445; 4,506,092; and 4,486,605. However, none of these methods are applicable to the general class of 2-naphthanoic acids or esters synthesized by the process of this invention.
Thus, there is still a need for a simple and general process for the synthesis of 2-naphthanoic acids and esters thereof having a predictable substitution pattern. The present invention enables such a synthesis through the preparation of substituted and unsubstituted 2-acetonaphthones which can be oxidized by conventional methods to the 2-naphthanoic acids or esters thereof.